1. Field of the Invention
The present invention relates to light emitting display devices. More particularly, the present invention relates to an organic light emitting display device and a method of fabricating the same.
2. Description of the Related Art
The organic light emitting display device, a self-emissive display device, has an ideal structure which is thin and lightweight, made of simple components and has a simple manufacturing process. The organic light emitting display device has advantages of wide viewing angle, high picture quality, excellent display of motion pictures, high color purity, and low power consumption and low driving electric current suitable for mobile devices.
Conventional organic light emitting display devices include a substrate, a pixel electrode disposed on the substrate, an organic layer including an emission layer (EML) disposed on the pixel electrode, and a counter electrode disposed on the organic layer. The organic layer may include a hole injection layer (HIL) and a hole transport layer (HTL) disposed between the pixel electrode and the EML, and an electron transport layer (ETL) and an electron injection layer (EIL) disposed between the EML and the counter electrode.
Driving the conventional organic light emitting display device may be performed as follows. By applying electric current between the pixel electrode and the counter electrode, holes are injected from the pixel electrode into the EML via the HIL and the HTL, and electrons are injected from the counter electrode into the EML via the EIL and the ETL. The holes and electrons injected into the EML are recombined in the EML to create excitons. Light is emitted while the excitons transition from an excited state to a ground state.
In general, a conventional top emitting organic light emitting display device uses a light resonance effect so that it is important to match the thickness of the pixel electrode and the thicknesses of the HIL and HTL disposed between the EML and the pixel electrode with a possible wavelength band. The HIL enhances power consumption efficiency and the lifespan of the organic light emitting display device by facilitating the injection of holes from the pixel electrode, which is an anode. The HTL increases hole mobility and the probability of forming excitons by easily transporting holes and confining electrons to the emission region.
However, when the conventional organic layer of the organic light emitting display device is formed thinly to extend the lifespan of the device, there is a high probability of dark pixels being generated due to particles. On the other hand, when the conventional organic layer is formed thickly to reduce dark pixels, driving electric current increases while efficiency and lifespan decrease. Thus, it is difficult to form the organic layer to have an appropriate thickness.